Acoustic device



c 1927 c. R. MOORE ACOUSTIC DEVICE Filed Dec. 8. 1922 2 Sheets-Sheet lMvemok: Char/es R. Moo/e. -&

y A/A Oct. 11, 1927. 88 C. R. MOORE ACOUSTIC DEVICE Filed Dec. 8. 1922 2Sheets-Sheet 2 //7 verv f0: Char/e5 /7. Moore.

Patented Oct. '11, 1927.

f UNITED STATES- 1,644,788 PATENT OFFICE.

CHARLES R. MOORE, OF WYOMING, NEW JERSEY,'ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

acousrrc DEVICE.

Application filed December 8, 1922. Serial No. 605,654.

This invention relates to acoustic devices and its object is to producea vibrating system for acoustic devices capable of accurately respondingto, and reproducing without loss of quality or volume, vibrations of thefrequency of ordinarysounds.

In general the invention comprises a. small rigid diaphragm, aperiodicin character, with means which loosely support it and control itsmovements. More specificall the inve ntion comprises the use of a sma lrigid diaphragm of light solid material and having a double convexsurface mountedbetween cushions of paper oraluminum foil annuhwhich'loosely support the diaphragm at ts edges and produce a dampingeffect upon its movements.

In the drawings z Fig. 1 is a cross section of a loud speaking receiverembodying the invention.

Fi 2 is an exploded detail view of the diap ragm and itsdamping members.

Figs. 3. and 4 show an application of'the invention to a phonographreproducer.

Supported on a mounting 5 is a plate 6 provided with an outwardly proect1ng flange 7 which isboth internally and externally threaded. Theflange 7 has an opening communicating with a born 8, and 'is providedwith a seat 9. Closing the opening in the flange is a ri id diaphragm,or plunger, 10. Interposed between the. diaphragm 10 and the seat 9 IS acushion of annuli 11 of thin material, such as aluminum foil or aper,and disposed against the opposite si e of diaphragm 10 IS a cushion ofsimilar annuli 21. plate 6 secured the diaphragm 10 and the washers 11and 21 in position. The diaphragm 10 is preferably made of a very lightmaterial, such as aluminum or phenol plastic compound, and ,is soproportioned as to be substantially rigid and movable as a plunger inresponse to vibrations of ordinary sound frequency. In order to permitsubstantially free movement of the diaphragm 10, the

.space between the nut 12 and the seat 9 is Somewhat greater than thetotal thickness of annuli 11 and 21', and the diaphragm 10 at itsperiphery. A space about 50% greater than the combined thickness of theannuli and the diaphra m has been found to give A nut 12 engaging the.

means such as the ma netic system 1..- through rod 14 to the diaphragm.The mag netic system 13 may. be of any suitable type such as that shownin Patent No. 1,365,898. of January 18, 1921, to H. G. Egerton. Inaddition to' forming a flexible support for the rigid dia hragm 10, theannuli also provide an air amping means of the t pe described in myPatent 1,583,416, of Iay 4, 1926, for damping out the effects ofresonance in any of the movin parts. Air damping is provided bythe airfilms, which owing to'the looseness of the annuli are formed betweenthem. Movements of the diaphragm cause the inward and the outward flowof the air between these annuli.

In Figs. 3 and 4, showing an application the reproducer 16 communicatingwith the usual tone arm 15, and the perforated cap 17 serves to hold theannuli 11 and 21, and diaphragm 10 in place. Vibrations on the record 20are transmitted to diaphragm 10 through the stylus 19 and st his arm 18in the usual manner. A rigid iaphragm airdamped at its peripher asdescribed, faithfully rep 'oduces recor ed sounds and practica leliminates the scratching noises so noticeable with the usual type ofreproducers;

The invention claimed is 1. An acoustic device comprising a small rigiddiaphragm positioned in a channel, and cushions of loosely held thinannuli positioned in said channel on both sides of said diaphragm forsupportin said (liaphragm at its edges and producing a damping effectupon its movement.

2. An acoustic device comprising a small rigid diaphragm positioned in achannel and cushions of looselyhcld thin annuli positioned in saidchannel on both sides of said diaphragm for supporting said diaphragm atits edges, said cushions comprising a plurality of sections whichoperate successively in series and all or part of which come into actiondepending upon the amplitude andthe frequency of vibration of thediaphragm.

3. In an acoustic device comprising. a small rigid diaphragm, means forposit1oning and damping said diaphragm consisting of a channelcontaining a plurality of thin annuli supporting the said diaphragm onboth sides at its periphery, thesaid annuli appl ing an impedance to thediaphragm whic changes with frequency.

4In an acoustic device comprising a small rigid diaphragm, means forpositioning and damping said diaphragm consisting of. a channel.containing a plurality of thin annuli supporting thesaid diaphragm onboth Sides at its periphery, the said aunuli applying an impedance tothe diaphragm which increases as .the frequency increases -and decreasesas the frequency decreases.

5. In an acoustic system comprising a small rigid diaphragm, asupporting channel, and means for supporting said diaphragm and dampingits movement consisting of thin annuli located on each side of 'saiddiaphragm. and lnounted loosely in said .'-:tn)portin channel.

.6. In an acoustic device comprising a smallrigid diaph'agin, supportingand damping means for said diaphragm for applying an impedance to thevibration of the diaphragm which changes with frequency,

comprising a mounting channel, and a pin rality of thin annuli locatedon each side of the diaphragm within said mounting channel, said annulibeing held by the said mounting channel loosely 'hutsufficiently closetogether to operatively preventair leaking from one side of thediaphragm to the other.

7. A small aperiodic diaphragm vibratahle as a whole, a mounting channeltherefor, and a plurality of thin ammli loosely disposed on each side ofsaid diaphragm near its periphenv and mounted in said channel,

the channetholding said annuli in axial CHARLES R. MOORE.

